/*
 * linux/fs/jbd/recovery.c
 *
 * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
 *
 * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * Journal recovery routines for the generic filesystem journaling code;
 * part of the ext2fs journaling system.
 */

#ifndef __KERNEL__
#include "jfs_user.h"
#else
#include <linux/module.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/errno.h>
#include <linux/slab.h>
#endif

/*
 * Maintain information about the progress of the recovery job, so that
 * the different passes can carry information between them.
 */
struct recovery_info
{
    tid_t		start_transaction;
    tid_t		end_transaction;

    int		nr_replays;
    int		nr_revokes;
    int		nr_revoke_hits;
};

enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
static int do_one_pass(journal_t *journal,
                       struct recovery_info *info, enum passtype pass);
static int scan_revoke_records(journal_t *, struct buffer_head *,
                               tid_t, struct recovery_info *);

#ifdef __KERNEL__

/* Release readahead buffers after use */
static void journal_brelse_array(struct buffer_head *b[], int n)
{
    while (--n >= 0)
        brelse (b[n]);
}


/*
 * When reading from the journal, we are going through the block device
 * layer directly and so there is no readahead being done for us.  We
 * need to implement any readahead ourselves if we want it to happen at
 * all.  Recovery is basically one long sequential read, so make sure we
 * do the IO in reasonably large chunks.
 *
 * This is not so critical that we need to be enormously clever about
 * the readahead size, though.  128K is a purely arbitrary, good-enough
 * fixed value.
 */

#define MAXBUF 8
static int do_readahead(journal_t *journal, unsigned int start)
{
    int err;
    unsigned int max, nbufs, next;
    unsigned long blocknr;
    struct buffer_head *bh;

    struct buffer_head * bufs[MAXBUF];

    /* Do up to 128K of readahead */
    max = start + (128 * 1024 / journal->j_blocksize);
    if (max > journal->j_maxlen)
        max = journal->j_maxlen;

    /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
     * a time to the block device IO layer. */

    nbufs = 0;

    for (next = start; next < max; next++) {
        err = journal_bmap(journal, next, &blocknr);

        if (err) {
            printk (KERN_ERR "JBD: bad block at offset %u\n",
                    next);
            goto failed;
        }

        bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
        if (!bh) {
            err = -ENOMEM;
            goto failed;
        }

        if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
            bufs[nbufs++] = bh;
            if (nbufs == MAXBUF) {
                ll_rw_block(READ, nbufs, bufs);
                journal_brelse_array(bufs, nbufs);
                nbufs = 0;
            }
        } else
            brelse(bh);
    }

    if (nbufs)
        ll_rw_block(READ, nbufs, bufs);
    err = 0;

failed:
    if (nbufs)
        journal_brelse_array(bufs, nbufs);
    return err;
}

#endif /* __KERNEL__ */


/*
 * Read a block from the journal
 */

static int jread(struct buffer_head **bhp, journal_t *journal,
                 unsigned int offset)
{
    int err;
    unsigned long blocknr;
    struct buffer_head *bh;

    *bhp = NULL;

    if (offset >= journal->j_maxlen) {
        printk(KERN_ERR "JBD: corrupted journal superblock\n");
        return -EIO;
    }

    err = journal_bmap(journal, offset, &blocknr);

    if (err) {
        printk (KERN_ERR "JBD: bad block at offset %u\n",
                offset);
        return err;
    }

    bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
    if (!bh)
        return -ENOMEM;

    if (!buffer_uptodate(bh)) {
        /* If this is a brand new buffer, start readahead.
                   Otherwise, we assume we are already reading it.  */
        if (!buffer_req(bh))
            do_readahead(journal, offset);
        wait_on_buffer(bh);
    }

    if (!buffer_uptodate(bh)) {
        printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
                offset);
        brelse(bh);
        return -EIO;
    }

    *bhp = bh;
    return 0;
}


/*
 * Count the number of in-use tags in a journal descriptor block.
 */

static int count_tags(struct buffer_head *bh, int size)
{
    char *			tagp;
    journal_block_tag_t *	tag;
    int			nr = 0;

    tagp = &bh->b_data[sizeof(journal_header_t)];

    while (((int)(tagp - bh->b_data) + (int)sizeof(journal_block_tag_t)) <= size) {
        tag = (journal_block_tag_t *) tagp;

        nr++;
        tagp += sizeof(journal_block_tag_t);
        if (!(tag->t_flags & cpu_to_be32(JFS_FLAG_SAME_UUID)))
            tagp += 16;

        if (tag->t_flags & cpu_to_be32(JFS_FLAG_LAST_TAG))
            break;
    }

    return nr;
}


/* Make sure we wrap around the log correctly! */
#define wrap(journal, var)						\
do {									\
	if (var >= (journal)->j_last)					\
		var -= ((journal)->j_last - (journal)->j_first);	\
} while (0)

/**
 * journal_recover - recovers a on-disk journal
 * @journal: the journal to recover
 *
 * The primary function for recovering the log contents when mounting a
 * journaled device.
 *
 * Recovery is done in three passes.  In the first pass, we look for the
 * end of the log.  In the second, we assemble the list of revoke
 * blocks.  In the third and final pass, we replay any un-revoked blocks
 * in the log.
 */
int journal_recover(journal_t *journal)
{
    int			err;
    journal_superblock_t *	sb;

    struct recovery_info	info;

    memset(&info, 0, sizeof(info));
    sb = journal->j_superblock;

    /*
     * The journal superblock's s_start field (the current log head)
     * is always zero if, and only if, the journal was cleanly
     * unmounted.
     */

    if (!sb->s_start) {
        jbd_debug(1, "No recovery required, last transaction %d\n",
                  be32_to_cpu(sb->s_sequence));
        journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
        return 0;
    }

    err = do_one_pass(journal, &info, PASS_SCAN);
    if (!err)
        err = do_one_pass(journal, &info, PASS_REVOKE);
    if (!err)
        err = do_one_pass(journal, &info, PASS_REPLAY);

    jbd_debug(1, "JBD: recovery, exit status %d, "
              "recovered transactions %u to %u\n",
              err, info.start_transaction, info.end_transaction);
    jbd_debug(1, "JBD: Replayed %d and revoked %d/%d blocks\n",
              info.nr_replays, info.nr_revoke_hits, info.nr_revokes);

    /* Restart the log at the next transaction ID, thus invalidating
     * any existing commit records in the log. */
    journal->j_transaction_sequence = ++info.end_transaction;

    journal_clear_revoke(journal);
    sync_blockdev(journal->j_fs_dev);
    return err;
}

/**
 * journal_skip_recovery - Start journal and wipe exiting records
 * @journal: journal to startup
 *
 * Locate any valid recovery information from the journal and set up the
 * journal structures in memory to ignore it (presumably because the
 * caller has evidence that it is out of date).
 * This function does'nt appear to be exorted..
 *
 * We perform one pass over the journal to allow us to tell the user how
 * much recovery information is being erased, and to let us initialise
 * the journal transaction sequence numbers to the next unused ID.
 */
int journal_skip_recovery(journal_t *journal)
{
    int			err;
    journal_superblock_t *	sb;

    struct recovery_info	info;

    memset (&info, 0, sizeof(info));
    sb = journal->j_superblock;

    err = do_one_pass(journal, &info, PASS_SCAN);

    if (err) {
        printk(KERN_ERR "JBD: error %d scanning journal\n", err);
        ++journal->j_transaction_sequence;
    } else {
#ifdef CONFIG_JBD_DEBUG
        int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
        jbd_debug(1,
                  "JBD: ignoring %d transaction%s from the journal.\n",
                  dropped, (dropped == 1) ? "" : "s");
#endif
        journal->j_transaction_sequence = ++info.end_transaction;
    }

    journal->j_tail = 0;
    return err;
}

static int do_one_pass(journal_t *journal,
                       struct recovery_info *info, enum passtype pass)
{
    unsigned int		first_commit_ID, next_commit_ID;
    unsigned long		next_log_block;
    int			err, success = 0;
    journal_superblock_t *	sb;
    journal_header_t *	tmp;
    struct buffer_head *	bh;
    unsigned int		sequence;
    int			blocktype;

    /* Precompute the maximum metadata descriptors in a descriptor block */
    int			MAX_BLOCKS_PER_DESC;
    MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
                           / sizeof(journal_block_tag_t));

    /*
     * First thing is to establish what we expect to find in the log
     * (in terms of transaction IDs), and where (in terms of log
     * block offsets): query the superblock.
     */

    sb = journal->j_superblock;
    next_commit_ID = be32_to_cpu(sb->s_sequence);
    next_log_block = be32_to_cpu(sb->s_start);

    first_commit_ID = next_commit_ID;
    if (pass == PASS_SCAN)
        info->start_transaction = first_commit_ID;

    jbd_debug(1, "Starting recovery pass %d\n", pass);

    /*
     * Now we walk through the log, transaction by transaction,
     * making sure that each transaction has a commit block in the
     * expected place.  Each complete transaction gets replayed back
     * into the main filesystem.
     */

    while (1) {
        int			flags;
        char *			tagp;
        journal_block_tag_t *	tag;
        struct buffer_head *	obh;
        struct buffer_head *	nbh;

        cond_resched();

        /* If we already know where to stop the log traversal,
         * check right now that we haven't gone past the end of
         * the log. */

        if (pass != PASS_SCAN)
            if (tid_geq(next_commit_ID, info->end_transaction))
                break;

        jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
                  next_commit_ID, next_log_block, journal->j_last);

        /* Skip over each chunk of the transaction looking
         * either the next descriptor block or the final commit
         * record. */

        jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
        err = jread(&bh, journal, next_log_block);
        if (err)
            goto failed;

        next_log_block++;
        wrap(journal, next_log_block);

        /* What kind of buffer is it?
         *
         * If it is a descriptor block, check that it has the
         * expected sequence number.  Otherwise, we're all done
         * here. */

        tmp = (journal_header_t *)bh->b_data;

        if (tmp->h_magic != cpu_to_be32(JFS_MAGIC_NUMBER)) {
            brelse(bh);
            break;
        }

        blocktype = be32_to_cpu(tmp->h_blocktype);
        sequence = be32_to_cpu(tmp->h_sequence);
        jbd_debug(3, "Found magic %d, sequence %d\n",
                  blocktype, sequence);

        if (sequence != next_commit_ID) {
            brelse(bh);
            break;
        }

        /* OK, we have a valid descriptor block which matches
         * all of the sequence number checks.  What are we going
         * to do with it?  That depends on the pass... */

        switch (blocktype) {
        case JFS_DESCRIPTOR_BLOCK:
            /* If it is a valid descriptor block, replay it
             * in pass REPLAY; otherwise, just skip over the
             * blocks it describes. */
            if (pass != PASS_REPLAY) {
                next_log_block +=
                    count_tags(bh, journal->j_blocksize);
                wrap(journal, next_log_block);
                brelse(bh);
                continue;
            }

            /* A descriptor block: we can now write all of
             * the data blocks.  Yay, useful work is finally
             * getting done here! */

            tagp = &bh->b_data[sizeof(journal_header_t)];
            while (((int)(tagp - bh->b_data) + (int)sizeof(journal_block_tag_t))
                    <= journal->j_blocksize) {
                unsigned long io_block;

                tag = (journal_block_tag_t *) tagp;
                flags = be32_to_cpu(tag->t_flags);

                io_block = next_log_block++;
                wrap(journal, next_log_block);
                err = jread(&obh, journal, io_block);
                if (err) {
                    /* Recover what we can, but
                     * report failure at the end. */
                    success = err;
                    printk (KERN_ERR
                            "JBD: IO error %d recovering "
                            "block %ld in log\n",
                            err, io_block);
                } else {
                    unsigned long blocknr;

                    J_ASSERT(obh != NULL);
                    blocknr = be32_to_cpu(tag->t_blocknr);

                    /* If the block has been
                     * revoked, then we're all done
                     * here. */
                    if (journal_test_revoke
                            (journal, blocknr,
                             next_commit_ID)) {
                        brelse(obh);
                        ++info->nr_revoke_hits;
                        goto skip_write;
                    }

                    /* Find a buffer for the new
                     * data being restored */
                    nbh = __getblk(journal->j_fs_dev,
                                   blocknr,
                                   journal->j_blocksize);
                    if (nbh == NULL) {
                        printk(KERN_ERR
                               "JBD: Out of memory "
                               "during recovery.\n");
                        err = -ENOMEM;
                        brelse(bh);
                        brelse(obh);
                        goto failed;
                    }

                    lock_buffer(nbh);
                    memcpy(nbh->b_data, obh->b_data,
                           journal->j_blocksize);
                    if (flags & JFS_FLAG_ESCAPE) {
                        *((__be32 *)bh->b_data) =
                            cpu_to_be32(JFS_MAGIC_NUMBER);
                    }

                    BUFFER_TRACE(nbh, "marking dirty");
                    set_buffer_uptodate(nbh);
                    mark_buffer_dirty(nbh);
                    BUFFER_TRACE(nbh, "marking uptodate");
                    ++info->nr_replays;
                    /* ll_rw_block(WRITE, 1, &nbh); */
                    unlock_buffer(nbh);
                    brelse(obh);
                    brelse(nbh);
                }

skip_write:
                tagp += sizeof(journal_block_tag_t);
                if (!(flags & JFS_FLAG_SAME_UUID))
                    tagp += 16;

                if (flags & JFS_FLAG_LAST_TAG)
                    break;
            }

            brelse(bh);
            continue;

        case JFS_COMMIT_BLOCK:
            /* Found an expected commit block: not much to
             * do other than move on to the next sequence
             * number. */
            brelse(bh);
            next_commit_ID++;
            continue;

        case JFS_REVOKE_BLOCK:
            /* If we aren't in the REVOKE pass, then we can
             * just skip over this block. */
            if (pass != PASS_REVOKE) {
                brelse(bh);
                continue;
            }

            err = scan_revoke_records(journal, bh,
                                      next_commit_ID, info);
            brelse(bh);
            if (err)
                goto failed;
            continue;

        default:
            jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
                      blocktype);
            brelse(bh);
            goto done;
        }
    }

done:
    /*
     * We broke out of the log scan loop: either we came to the
     * known end of the log or we found an unexpected block in the
     * log.  If the latter happened, then we know that the "current"
     * transaction marks the end of the valid log.
     */

    if (pass == PASS_SCAN)
        info->end_transaction = next_commit_ID;
    else {
        /* It's really bad news if different passes end up at
         * different places (but possible due to IO errors). */
        if (info->end_transaction != next_commit_ID) {
            printk (KERN_ERR "JBD: recovery pass %d ended at "
                    "transaction %u, expected %u\n",
                    pass, next_commit_ID, info->end_transaction);
            if (!success)
                success = -EIO;
        }
    }

    return success;

failed:
    return err;
}


/* Scan a revoke record, marking all blocks mentioned as revoked. */

static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
                               tid_t sequence, struct recovery_info *info)
{
    journal_revoke_header_t *header;
    int offset, max;

    header = (journal_revoke_header_t *) bh->b_data;
    offset = sizeof(journal_revoke_header_t);
    max = be32_to_cpu(header->r_count);

    while (offset < max) {
        unsigned long blocknr;
        int err;

        blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
        offset += 4;
        err = journal_set_revoke(journal, blocknr, sequence);
        if (err)
            return err;
        ++info->nr_revokes;
    }
    return 0;
}
